The invention relates to nonfelting wool and to a process for producing it by (a) a plasma treatment of the wool and (b) an after-treatment with aqueous dispersions of self-dispersing isocyanates.
The textile processing industry has a particular interest in reducing the felting tendency of wool, especially of raw wool or unprocessed wool. The felting of wool is customarily reduced by finishing with specific auxiliaries.
Isocyanates for the antifelt finishing of textiles are well known and can be used, for example, as described in DE-A 1,904,802, in organic solvents or, as described in DE-A 1,769,121, in aqueous dispersion with the aid of emulsifiers. Both organic solvents and possibly water-polluting emulsifiers are today no longer appropriate for ecological and occupational hygiene reasons. Prior artisans therefore developed self-dispersing isocyanates and also formulations containing very low levels of solvents or emulsifiers as auxiliaries and additives.
DE-A 1,794,221 describes the treatment of fiber materials with isocyanate prepolymers which still contain free isocyanate groups. This finishing process can take place in solvents such as perchloroethylene or in aqueous emulsion by using auxiliary emulsifiers.
U.S. Pat. No. 3,847,543 discloses a process for the antifelt finishing of wool using an aqueous dispersion simultaneously containing aliphatic isocyanates, OH-functional crosslinkers, and organometallic catalysts. Although this process takes place in an aqueous phase, auxiliary solvents and emulsifiers continue to be required.
DE-A 2,657,513 describes a process for the antifelt finishing of wool by treating the wool yarn with an aqueous liquor that contains the felt-proofing agent. The feltproofing agents used are reactive polyolefins, reaction products of polyisocyanates and hydroxyl compounds, silicone polymers, aziridine compounds, reaction products of epoxides with fatty amines and dicarboxylic acids or polyamides, reaction products with thiosulfate end groups, or, preferably, reaction products with mercapto end groups.
WO 95/30045 describes a process utilizing specific isocyanates for the antifelt finishing of wool. No solvents or emulsifiers are needed because the isocyanates used are water-dispersible. The wool is first subjected to a pretreatment with oxidizing agents, followed by a reductive treatment, before the water-dispersible isocyanates are used. The disadvantage with this process is that the oxidative and reductive pretreatment gives rise to wastewaters that must be properly neutralized and treated.
The prior art further includes another method for the antifelt finishing of wool where the wool is treated with a plasma. DE-A 4,344,428 discloses, for example, a process in which the wool is subjected to an antifelt finish comprising a combination of plasma or corona pretreatment and enzymatic aftertreatment. The wool is sensitized with a solution that contains sulfide ions prior to the enzyme treatment.
DE 196 16 776 Cl further describes a process for the antifelt finishing of wool where moist wool material having a water content of 4 to 40% by weight is exposed to a low pressure plasma treatment before being further processed into textile fabrics or sheets. The wool is subjected to a radio frequency discharge at a frequency of 1 kHz to 3 GHz and a power density of 0.001 to 3 W/cm.sup.3 at a pressure of 10.sup.-2 to 10 mbar for a period of 1 to 600 sec in the presence or absence of non-polymerizing gases. The disadvantage with this process is the complicated equipment. Specific vacuum pumps are needed, and vacuum locks must be fitted so that the material may enter and exit without streaming.
The German Patent Application bearing the file reference 197 36 542.6 (unpublished at the priority date of the present invention) discloses a process for the antifelt finishing of wool in which the wool is initially likewise pretreated with a low pressure plasma and subsequently aftertreated with aqueous dispersions of self-dispersing isocyanates. Again, the equipment needed for the low pressure plasma treatment is a disadvantage.
The invention has for its object to provide by a technically improved process nonfelting wool which after further processing into made-up merchandise does not felt and shrink in machine washing.